﻿using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Web;

namespace Jimmy.Helper
{
    public static class ClientHelper
    {
        /// <summary>
        /// 获取客户端IP地址
        /// </summary>
        /// <returns>若失败则返回回送地址</returns>
        public static string GetIP()
        {
            try
            {
                //如果客户端使用了代理服务器，则利用HTTP_X_FORWARDED_FOR找到客户端IP地址
                string userHostAddress = HttpContext.Current.Request.ServerVariables["HTTP_X_FORWARDED_FOR"].ToString().Split(',')[0].Trim();
                //否则直接读取REMOTE_ADDR获取客户端IP地址
                if (string.IsNullOrEmpty(userHostAddress))
                {
                    userHostAddress = HttpContext.Current.Request.ServerVariables["REMOTE_ADDR"];
                }
                //前两者均失败，则利用Request.UserHostAddress属性获取IP地址，但此时无法确定该IP是客户端IP还是代理IP
                if (string.IsNullOrEmpty(userHostAddress))
                {
                    userHostAddress = HttpContext.Current.Request.UserHostAddress;
                }
                //最后判断获取是否成功，并检查IP地址的格式（检查其格式非常重要）
                if (!string.IsNullOrEmpty(userHostAddress) && IsIP(userHostAddress))
                {
                    return userHostAddress;
                }
                return "127.0.0.1";
            }
            catch
            {
                return "127.0.0.1";
            }
        }

        /// <summary>
        /// 检查IP地址格式
        /// </summary>
        /// <param name="ip"></param>
        /// <returns></returns>
        public static bool IsIP(string ip)
        {
            return System.Text.RegularExpressions.Regex.IsMatch(ip, @"^((2[0-4]\d|25[0-5]|[01]?\d\d?)\.){3}(2[0-4]\d|25[0-5]|[01]?\d\d?)$");
        }
    }
}
